Heretofore, vehicles for the parenteral administration of many fat-soluble pharmaceutically active materials were not readily available. In addition, when such vehicles were prepared, their parenteral administration often resulted in many undesirable side-effects such as hemolysis, phlebothromboses or blood coagulation.
Parenteral administration of fat-soluble pharmaceutically active material has been achieved using liposome solutions. In these compositions, the active materials can be parenterally administered without the above undesirable side-effects and without any loss in their biological activity.
The preparation of pharmaceutically acceptable liposome solutions has been known for some time. Information about such compositions have been presented by G. Gregoriadis ("Liposomes or Drug Carriers in Biology and Medicine") and B. E. Ryman ("Liposome Delivery of Materials of Therapeutic Interest--Possibilities and Problems") in the Abstracts of the symposium entitled "The Potential of Liposomes as Drug Carriers", Battelle Institute, Geneva, Switzerland, March, 1978, pp. 5-11 and 26-31. However, difficulties were and continue to be encountered with the long term stability of such solutions. Stability of such solutions depends on both the composition of the lipid phase and the composition of the aqueous phase. In addition, the presence of even minor impurities in the solutions can lead to floculation.
It has now been found that stable liposome solutions suitable for parenteral administration can be prepared by the addition of sugars to the liposome solutions as protective colloids.